Production interface for integrated circuit test system

ABSTRACT

A production operator interface is created using self-contained ActiveX controls each of which provide an interface to a specific part of the overall test system. These controls all communicate among themselves automatically. The production interface uses an ActiveX &#34;tester control&#34; which provides an application programming interface to the rest of the software control system. A library of self-contained ActiveX controls is provided which contains &#34;operator controls&#34; which may be &#34;dragged and dropped&#34; into an operator window to provide the operator with information and the ability to control the test system. In addition a semiconductor test system needs to be adapted to work with one or more different packaged device handlers or wafer probers which position a semiconductor device for testing by the tester. An ActiveX operator control allows an operator to select a handler driver from a library of handler drivers.

BACKGROUND IF THE INVENTION

1. Field of the Invention

This invention relates generally to automatic test equipment used in themanufacture of semiconductors and more specifically to the productioninterface and handler drivers of the test system.

2. Description of the Related Art

Automatic test equipment is widely used in the manufacture ofsemiconductors. Semiconductors are generally tested at least once duringtheir manufacture and are sometimes tested at more than one step in themanufacturing process. Because every component is tested, speed oftesting is critical to the economic manufacture of semiconductors. Slowtesting prevents full utilization of the expensive capital equipmentneeded to produce semiconductor components. Modern semiconductorcomponents are very complicated and have many operating states. Each ofthese operating states must be exercised to perform a complete test.Automatic test equipment is therefore designed to apply test data to asemiconductor device and make numerous measurements very quickly in aproduction setting.

FIG. 1 shows a generalized automatic test system of the prior art. Toprovide thorough and fast testing, the automatic test system generallyincludes a tester body 112, a computerized work station 110 and ahandling device 114. The computer work station 110 controls both thehandling device 114 and the tester body 112. It controls the handlingdevice 114 to position the semiconductor device (not shown) where itmakes contacts with numerous test probes 118 on the tester body 112.Often, a tester will include a separate test head containing test probes118. However, such a distinction is not important for the invention.

Workstation 110 then controls tester body 112 to run a series of testson the device under test. Each test generally includes a setup portionin which control signals are sent from the work station 110 to thetester body 112. The control signals are usually digital values sentover bus 116. These control signals configure the hardware within testerbody 112 to make the measurements required for the test. The hardwarewithin the tester body provides stimulus and measures responses from thedevice under test in accordance with the control signals.

FIG. 1 shows that the hardware within tester body 112 includes numerouscircuits identified as pins 124. Each pin 124 generates signals or makesmeasurements for one of the test probes 118. Each pin might provide ormeasure a static, or DC, signal. Alternatively, each pin 124 mightprovide or measure changing data in what is sometimes called a "burst".

During a burst, tester body 120 is controlled by timing and sequencingcircuit 120. Timing and sequencing circuit 120 causes each of the pins124 to read a sequence of data values from an associated memory 128.Each data value indicates the type of signal the pin should apply orexpect to measure at its associated test probe 118 at a specific pointin time. If the pin compares a measurement to an expected value, theresults might also be stored in memory 128.

The set of data values that define the values all the pins 124 shouldprovide or expect to measure at one time is called a "vector." During aburst, many vectors are executed. The vectors must be executed at a veryhigh rate to simulate actual operating conditions of the device undertest. There are usually millions of vectors to define the bursts neededto test a semiconductor device. The vectors are typically loaded intomemories 128 at the time test system is programmed to test a particulartype of part. This loading process might take several minutes and is notrepeated for each burst. Rather, for each burst, work station 110 sendscommands indicating which vectors are to be executed as part of theburst. Once the burst is completed, work station 110 reads the resultsof the burst from memory 128 or timing and sequencing circuit 120.

In addition, tester body 112 includes one or more instruments 126. Aninstrument performs a specific test function. It might for examplegenerate a specific test signal such as a sine wave. Alternatively, aninstrument might sample a signal at a high rate so that it can later beanalyzed by a digital signal processor. These functions might beperformed as part of a burst or might be performed separate from aburst.

A full test of a part, sometimes called a "job", will consist of aseries of bursts interspersed with DC measurements or measurements byinstruments 126. The bursts might be used to measure specific functionalattributes of the device under test. Alternatively, each burst might beused only to place the device under test into a state in which a DCmeasurement can be taken. The order in which these elements of a testare performed, sometimes called the "flow," is dictated by software inworkstation 110.

Once a device has been fully tested, or tested to the point where it isdetermined to be defective, work station 110 generates control signalsto the handling device 114. Handling device 114 then presents the nextdevice to be tested to tester body 112 and the process is repeated.Work-station 110 also gathers data about whether particular devicespassed or failed. It can process this data so that defective devices arediscarded or it can perform other functions, such as analyzing the datafor failure trends.

For production it is highly desirable that the software that allows anoperator to control the tester be very easy to learn and use. What isneeded in a production test environment, is a very simple operatorinterface interface to the rest of the test system. In addition theinterface must be flexible and easy to change because of the many variedrequirements of this interface from customer to customer.

SUMMARY OF THE INVENTION

The present invention provides a method to create a simple operatorinterface to the test system that is very flexible. A productionoperator interface is created using self-contained ActiveX controls eachof which provide an interface to a specific part of the overall testsystem. These controls all communicate among themselves automatically.The production interface uses an ActiveX "tester control" which providesan application programming interface to the rest of the software controlsystem. A library of self-contained ActiveX controls is provided whichcontains "operator controls" which may be "dragged and dropped" into anoperator window to provide the operator with information and the abilityto control the test system. The ActiveX operator controls interfacethrough the ActiveX tester control to the rest of the test system.

In addition a semiconductor test system needs to be adapted to work withone or more different packaged device handlers or wafer probers whichposition a semiconductor device for testing by the tester. An ActiveXoperator control allows an operator to select a handler driver from alibrary of handler drivers. Each handler driver uses an ActiveX handlertester control which serves as the interface between the handler and theActiveX tester control (and thus to the rest of the test system).

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a hardware block diagram of a prior art tester.

FIG. 2 is a functional block diagram of the Production Interface of thepresent invention.

FIG. 3 is an example of a very simple Production Operator Interface.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 is a detailed functional block diagram of the complete testsystem of the present invention. The system includes a PC workstation2000, tester 2002, a handler 2004, and a host 2006. The software ofworkstation 2000 is made up of a production interface 2008 and testdevelopment and execution program 2010 (generically called a softwarecontrol system).

Production interface 2008, serves as the interface between the operatorand test development and execution program 2010, host 2006 and handler2004. To control this equipment in a production test environment, it isnecessary to provide a very simple control interface to the equipmentoperator. However, there are many varied requirements of this interfacefrom customer to customer and even site to site within the samecustomer. In addition, the test equipment must often interface to othercomputer control systems with a variety of requirements. Providing aninterface that is simple yet flexible, which meets the requirements ofall users, and can be interfaced to other computer control programs hasbeen a very difficult problem. This was all previously programmed inC/C++.

Production interface 2008 solves the problem through the use of selfcontained control objects hereinafter called self contained "controls"each of which provides an interface to a specific part of the overalltest system including test development and execution program 2010, host2006, and handler drivers 2024. These controls all communicate amongthemselves automatically.

In the preferred embodiment, these controls are "ActiveX" controlswritten in Visual Basic (hereinafter VB) from Microsoft Corporation ofRedmond, Wash. These controls can be combined quickly and easily into agraphical user interface (GUI) using Visual Basic or can be used as aprogrammatic interface without a GUI. The Active X controls allow theoperator to initiate an action in test development and execution program2010, host 2000, or handler 2004. The operator during production testinguses an active X control to communicate with executive 2016. Inaddition, the operator may initiate accompanying actions by the handler2004 and the host 2006 or the production interface may automaticallyinitiate action in test development and execution program 2010 (throughexecutive 2016) in response to requests from Handler 2004 or Host 2006.

An ActiveX control interface is defined by properties, events, andmethods. A method is a Visual Basic function that may be called in thecontrol. The function can take arguments and return a value, and isanalogous to a function definition in a C/C++ library. A property isbasically a global variable in the control, with access functionsprovided to get and/or set its value. Properties can be madeprogrammable at design time or run time, and VB automatically handlessaving programmed property values as part of the production interfaceexecutable. An event is a signal initiated by the control that is passedto the object containing the control. The container (the productioninterface in the preferred embodiment) can include a handler for theevent if it is needed.

There are four types of ActiveX controls in the preferred embodiment:

Tester Control 2014. This provides an application programming interface(API) to the rest of the system.

Operator controls 2022. These are GUI components that allow an operatorat the tester console to perform actions or view status.

Handler Tester Control 2026. This is an ActiveX control that defines theinterface to any handler 2004. This serves as the single connectionpoint between the handler driver 2024 and the Tester Control 2014 of theproduction interface. Anything containing this control can be used as ahandler driver 2024 by production interface 2008.

Host interface control 2021. This control translates the Tester Control2014 API into standard messages sent to or received from host 2006.

The term production controls refers to all ActiveX controls used tocreate a production operator interface and/or handler driver. Thisincludes the tester control, operator controls, handler tester controland host interface controls.

To operate the tester in a semiconductor production environment thereneeds to be a variety of windows available that the operator may bringup on his display depending on the test to be performed. To create thesewindows the programmer can "drag and drop" controls from a library ofActiveX controls onto the operator window. ActiveX controls are designedto be self-contained so that they may be dragged and dropped into anyapplication. The term "drag and drop" is used generically to refer tothe act of selecting an object and placing that object into a container.The term container is used generically to refer to an entity that cancontain other objects. In the preferred embodiment the container is theoperator window and the objects are ActiveX controls. The advantage isthe simplicity with which the different windows at the operatorinterface may be created. Previously, all such forms needed to beindividually programmed in C/C++ which was difficult and time consuming.It is a completely novel application to use ActiveX controls foroperator controls in semiconductor testing.

Another advantage is the manner in which the ActiveX controls on aspecific window at the operator station all talk to each other. EachActiveX control is designed to operate such that at the time ofinitialization each operator control will search for other operatorcontrols and the tester control in the window and establish acommunication link to every other ActiveX control such that each controlcan talk to each other control.

To further illustrate, an example production operator interface is shownin FIG. 3. Operator Interface 3000 contains a tester control 3030, a bindisplay 3010, and a start button 3020. The bin display and start buttonare examples of operator controls. An example of the search routine isthat used to identify all bin displays in the window is given below. Themethod used is to iterate through all controls in the parent windowlooking for controls of type "BinDisplay". When a bin display is found,an object handle for that control is saved for future communication withthe bin displays. This search routine was difficult to determine and thefollowing program written in visual basic is the best mode known for thesearch.

    ______________________________________                                         .sup. Note 1:                                                                       This routine currently looks up exactly one level, it                  '      should be extended to walk through an arbitrary number of              '      levels.                                                                ' Note 2:                                                                            This routine is called whenever communication with a bin               '      display is needed (see note 3). Since the number of                    '      controls cannot change at run time (see note 4), for                   '      optimizes, if bin displays have already been found,                    '      the routine simply exits.                                              '                                                                             ' Note 3:                                                                            This routine is called multiple times because there is not             '      an appropriate initialization event for the user control               '      when it can be called. Neither UserControl.sub.-- Initialize or               UserControl.sub.-- InitProperties works for different reasons.         '      This should be corrected when possible.                                '                                                                             ' Note 4:                                                                            Controls can actually be added at run time. We are assuming            '      that this will not happen. This may not strictly be a safe             '      assumption.                                                              Private Sub BinDisplayInit( )                                               Dim thisControl As Object                                                      If Not IsEmpty(BinDisplayHandleSet) Then Exit Sub                             BinDisplayHandleSet = True                                                    FoundBinDisplays = False                                                      For Each thisControl In UserControl.Parent.Controls                            If TypeOf thisControl is BinDisplay Then                                      If FoundBinDisplays Then                                                       ReDim Preserve BinDisplayHandle(UBound(BinDisplayHandle) -                    LBound(BinDisplayHandle) + 1)                                                Else                                                                           ReDim BinDisplayHandle(1)                                                     FoundBinDisplays = True                                                      End If                                                                        Set BinDisplayHandle(UBound(BinDisplayHandle)) = thisControl                  End if                                                                       Next thisControl                                                             End Sub                                                                       ______________________________________                                    

As an example of how the ActiveX controls communicate with each other,when the operator wishes to initiate a test he will use an ActiveX startcontrol in operator controls 2022. The start control is programmed tocommunicate with a method in the ActiveX tester control 2014 that willinitiate the start of the test by the executive 2016. The test programwill run and a result will be available. The test development andexecution program 2010 will send back an indication that the test iscomplete. The tester control 2014 will request the results of the testfrom executive 2016. The tester control 2014 next will inform any bindisplays of the test results.

All of the ActiveX controls in the operator interface communicate to therest of the test system through the ActiveX tester control. There isonly one tester control 2014.

The operator controls 2022 also have an ActiveX handler control thatlets an operator select a handler from a menu of available handlerdrivers, connect it, and enable it. The term handlers is usedgenerically to refer to packaged device handlers or wafer probers. Thedesign of handler drivers 2024 is a major departure from what was donein the prior art. The handler support for these prior art testersconsists of a single, highly configurable library that attempts tosupport all possible equipment. This has proved to be difficult forcustomers to use. Configuring any particular piece of equipment iscomplicated because the interface has many programmable settings, onlysome of which are necessary. If a new handler requires a feature notavailable in the library, a system software update is required which theend customer can't do. And the library is bug-prone, since any change tosupport new handlers risks introducing bugs in preexisting ones.

In the preferred embodiment each handler has its own driver, containingonly the code necessary to operate that specific handler. At run time,the driver required to operate the handler in use is dynamically loadedinto the production interface. This has important advantages over theprior art approach:

Since each driver module has only the code it requires, it is muchsmaller and simpler.

The Visual Basic environment makes it easy for the field organization orcustomers themselves to create a new driver without requiring supportfrom the factory software group. The preferred embodiment includes anumber of drivers which can be copied as starting points.

There is little risk that software development for the invention willcause bugs, unlike with a single library which must be continuallychanged to add new features.

The preferred embodiment will provide a library of handler drivers whichcustomers can either use directly or as a base for developing a newdriver. To develop a new driver, the usual start is to copy one of thepreferred embodiment's drivers. The driver consists of a VB form thatcontains, at a minimum, a Handler Tester Control 2026 and calls to acommunications interface 2028. The Handler Tester Control 2026 definesthe interface to the handler 2004 . User-defined code uses the control'sproperties, events, and methods and also programs the handlerappropriately through the communications interface 2028.

More specifically, the Handler Tester Control 2026 is an ActiveX controlthat defines the interface to any handler 2004. This serves as thesingle connection point between the handler driver 2024 and the rest ofthe production interface 2008. Anything containing this control can beused by production interface 2008 as a handler driver 2024.

The communications interface 2028 defines the network transport layerbetween the Tester Control 2014 and any peripheral. The handler driver2024 uses one or more communication interfaces 2028 to do actual readsand writes to and from the handler or prober 2004.

Production interface 2008 also has an ActiveX host interface control2021 that allows the operator to connect the host 2006 to the tester2002. On the production floor, a tester 2002 is smetimes connected to ahost 2006 that monitors tester status, collects test results, and cancontrol the testing process directly.

The Host interface control 2021 translates the Tester Control 2014 APIinto standard messages sent to or received from host 2006. There are twoparts to the host interface control 2021. The Host Message Control 2030is responsible for translating the Tester Control 2014 API into messagesin a standard format that can be understood by the host. The NetworkInterface 2032 does the actual network communication with the hostmachine.

The Host Message Control 2030 is an ActiveX control which listens to theTester Control 2014 events and can execute its properties and methods.When a Tester Control 2014 event is received that requires a message tothe host 2006, it produces a host message describing the event andraises a "message ready" event. When a message is received from the host2006 via a "message received" method, it accesses the appropriate TesterControl methods and properties to implement the request. The networkinterface 2032 is handled by code in the production interface whichinteracts with the host message control.

Test development and execution program 2010 operates within the WindowsNT operating system and is made up of software divided into elementsthat are used 1) at test development and analysis time and 2) at testexecution time. Excel workbook 308 is the portion of the program used todevelop tests during test development and analysis time. Excel is aspreadsheet program that allows an application to be developed. VisualBasic is a programming language built into Excel that is used to writetest templates and to control execution of tests.

In the preferred embodiment the device data development and flowdevelopment tools 310 are implemented by customized spreadsheets withinthe Excel workbook 308. Three types of data need to be specified by thespreadsheets for a test: device data, test flow data, and test instancedata. For device data these may be spreadsheets for time sets, channelmaps, edge sets or a pinmap. Each of these spreadsheets is a dataset.The test instance data spreadsheets specify the test template and itsassociated device data set. A test template is a test algorithm. In thepreferred embodiment, test templates are written in Visual Basic. A testtemplate and its associated data set is called an "instance". Test flowdata may be spread sheets specifying a series of test steps that are tobe executed. The series of test steps may be the execution of a seriesof test templates each using an associated device data set.

Summarizing, the Excel spreadsheet information 312 includes the devicedata sets, the test instance information which defines which templatesare to be used with the associated data set, and the test flowinformation defining the sequence of test instances to be executed.

Test Templates 320 are written in Visual Basic and are normally providedby the manufacturer. The data device and flow development tools 310,Excel worksheets 312 and manufacturer provided test templates 320 areused during test development and analysis time prior to the time of testexecution during production testing. Test templates 320 and Excelworksheets 312 are used also during production testing.

The additional software of test development and execution program 2010that is used at test execution time during production testing is theexecutive 2016, flow control software 314, data manager 316, and devicedrivers 328. All of this software works in the Windows NT operatingsystem environment.

In the preferred embodiment, the tester control 2014 initiates theloading of the test program. Excel is started and the workbook 308 isopened up. The data from worksheets 312 go to data manager 316. Theexecutive 2016 responds to tester control 2014 and calls flow control314 and instrument drivers 328. They request data from the data manager316. The test is now ready to go and the all functions assume an idlestate. When the test program is ready to run, the tester control tellsthe executive 2016 to initiate the test. The executive tells flowcontrol 314 to execute the program. The flow control determines whichinstance to execute and calls a template from template library 320. Thetemplate requests the device data (i.e. arguments) from the data manager316 and then calls the drivers 328.

Device drivers 328 provide the signals to tester 2002 to perform a fulltest or "job" on a device under test (DUT). The full test will includeDC level, functional, and serial/scan testing of the DUT. The tester maybe any state of the art tester for a semiconductor. An example of atester is given in U.S. Pat. No. 5,606,568, assigned to the sameassignee Teradyne, which is hereby incorporated by reference.

After tester 2002 finishes the test the template determines whether thetest passes or fails and returns control to the flow control 314. Theflow control then determines if more instances need to be executed orwhether the flow is done. If the flow is done then the test systementers an idle state.

The Test Development and Execution Module 2010 is more fully disclosedin a co-pending patent application, assigned to the same assigneeTeradyne, entitled "LOW COST, EASY TO USE AUTOMATIC TEST SYSTEMSOFTWARE" to Daniel C. Proskauer and Predeep B. Deshpande, filed on Jun.13, 1997 and assigned Ser. No. 08/874,615, which is hereby incorporatedby reference.

Additional details of the production interface 2008, handler drivers2024, and host interface control 2022 are provided in the followingAPPENDIX A.

All rights including copyrights in the material contained in APPENDIX Aare vested in and the property of Teradyne, the assignee of the presentinvention. Teradyne retains and reserves all rights in APPENDIX A andgrants permission to reproduce the material only in connection withreproduction of the granted patent and for no other purpose.

While the preferred embodiments of the invention have been shown anddescribed, numerous variations and alternative embodiments will occur tothose skilled in the art. Accordingly, it is intended that the inventionbe limited only in terms of the appended claims. ##SPC1##

What is claimed is:
 1. A semiconductor test system comprising,a softwarecontrol system, a library of self-contained control objects, an operatorwindow, one or more of said self-contained control objects adapted tocreate a production interface to said software control system, saidproduction interface having 1) a self-contained tester control forproviding an application programming interface to said software controlsystem and 2) self-contained operator controls that provide an interfacebetween said operator window and said self-contained tester control,said self-contained operator controls in said library being "drag anddrop" controls adapted to be "dragged and dropped" into said operatorwindow.
 2. The semiconductor test system of claim 1 in which saidself-contained objects in said operator window all communicate with eachother.
 3. The semiconductor test system of claim 2 in which eachself-contained control object is designed to operate such that at thetime of initialization each self-contained control object will searchfor other self-contained control objects in the window and establish acommunication link to every other self-contained control object suchthat each self-contained control object can talk to each otherself-contained control object.
 4. The semiconductor test system of claim3 in which said self contained controls are ActiveX controls.
 5. Thesemiconductor test system of claim 4 in which said ActiveX controls areprogrammed in the Visual Basic programming language.
 6. Thesemiconductor test system of claim 2 in which said self contained testercontrol object and said self contained operator control objects are insaid operator window and communicate with each other.
 7. Thesemiconductor test system of claim 1 in which said operatorself-contained ActiveX controls in said operator window all communicatewith each other.
 8. The semiconductor test system of claim 6 in whicheach ActiveX control is adapted to operate such that at the time ofinitialization each ActiveX control will search for other ActiveXcontrols in the window and establish a communication link to every otherActiveX control such that each ActiveX control can talk to each otherActiveX control.
 9. A semiconductor test system comprising,a softwarecontrol system, a library of ActiveX controls, an operator window, oneor more of said ActiveX controls adapted to create a productioninterface to said software control system, said production interfacehaving 1) an ActiveX tester control for providing an applicationprogramming interface to said test program and 2) ActiveX operatorcontrols that provide an interface between said operator window and saidActiveX tester control, said ActiveX operator controls in said libraryadapted to be "dragged and dropped" into said operator window.
 10. Thesemiconductor test system of claim 9 in which said ActiveX controls insaid operator window all communicate with each other.
 11. Thesemiconductor test system of claim 10 in which each ActiveX control isadapted to operate such that at the time of initialization each ActiveXcontrol will search for other ActiveX controls in the window andestablish a communication link to every other ActiveX control such thateach ActiveX control can talk to each other ActiveX control.
 12. Thesemiconductor test system of claim 11 in which said ActiveX controls areprogrammed in the Visual Basic programming language.
 13. A semiconductortest system comprising,a semiconductor tester, a test development andexecution program for providing semiconductor device data parameter tosaid tester, an executive for initiating a test by said test developmentand execution program, a library of ActiveX controls, one or more ofsaid ActiveX controls adapted to create a production interface to saidexecutive, said production interface having 1) an ActiveX tester controlfor providing an application programming interface to said executive and2) ActiveX operator controls that provide an interface between anoperator window and said ActiveX tester control, said ActiveX operatorcontrols in said library adapted to be "dragged and dropped" into anoperator window, said ActiveX operator controls in said operator windowall communicating with each other.
 14. The semiconductor test system ofclaim 13 in which each ActiveX control is adapted to operate such thatat the time of initialization each ActiveX control will search for otherActiveX control on the window and establish a communication link toevery other ActiveX control such that each ActiveX control can talk toeach other ActiveX control.
 15. The semiconductor test system of claim14 in which said ActiveX controls are programmed in Visual Basicprogramming language.
 16. A semiconductor test system adapted to workwith one or more different handlers, said handlers for positioning asemiconductor device under test comprising,a library of handler drivers,each said handler driver adapted to work with a different handler, aproduction interface adapted to access said library, said productioninterface 1) having a tester self-contained control object for providingan application programming interface to said handler drivers and 2)having a self-contained operator control objects that provides aninterface between an operator window and said self-contained testercontrol object, said self-contained operator control object allowing anoperator to select a handler driver from said library of handlerdrivers.
 17. The semiconductor test system of claim 16 in which eachhandler driver has a self-contained handler tester control objectserving as the interface between said handler and said self-containedtester control object.
 18. The semiconductor test system of claim 17having a communications interface defining the communications networklayer between said handler and said handler tester control object. 19.The semiconductor test system of claim 18 in which said handler testercontrol object, said tester control object and said operator controlobject are ActiveX controls.
 20. The semiconductor test system of claim19 in which said ActiveX controls are written in the Visual Basicprogramming language.
 21. A semiconductor test system comprising,atester, a handler for positioning a semiconductor device to be tested bysaid tester, said handler being one of a plurality of handlers adaptedto work with said test system, a library of handler drivers, each saidhandler driver adapted to work with a different handler, a productioninterface adapted to access said library of handler drivers, saidproduction interface 1) having an ActiveX tester control for providingan application programming interface to said handler drivers and 2)having an ActiveX operator control that provides an interface between anoperator window and said ActiveX tester control, said ActiveX operatorcontrol allowing an operator to select a handler driver from saidlibrary of handler drivers.
 22. The semiconductor test system of claim21 in which each handler driver has an ActiveX handler tester controlserving as the interface between said handler and said ActiveX testercontrol.
 23. The semiconductor test system of claim 22 having acommunications interface defining the communications network layerbetween said handler and said ActiveX handler tester control.